<template>
    <div class="spec-preview">
        <img :src="skuImageList[index].imgUrl" />
        <div class="event" @mousemove="moveMask"></div>
        <div class="big">
            <img :src="skuImageList[index].imgUrl" :style="positionB" />
        </div>
        <div class="mask" :style="positionS"></div>
    </div>
</template>

<script>
export default {
    props: ["skuImageList"],
    name: "Zoom",
    data() {
        return {
            index: 0,
            positionS: {
                left: 0,
                top: 0,
            },
            positionB: {
                left: 0,
                top: 0,
            },
        };
    },
    beforeMount() {
        // 绑定一个全局事件
        this.$bus.$on("changeCurImg", this.changeImg);
    },
    beforeDestroy() {
        this.$bus.$off("changeCurImg");
    },
    methods: {
        changeImg(index) {
            this.index = index;
        },
        realDistance(distance, offset) {
            distance = distance < 0 ? 0 : distance;
            distance = distance > offset * 0.5 ? offset * 0.5 : distance;
            return distance;
        },
        moveMask(e) {
            let offset = e.target.clientWidth;
            let left = e.offsetX - offset * 0.25;
            left = this.realDistance(left, offset);
            let top = e.offsetY - offset * 0.25;
            top = this.realDistance(top, offset);
            this.positionS.left = left + "px";
            this.positionS.top = top + "px";
            this.positionB.left = -left * 2 + "px";
            this.positionB.top = -top * 2 + "px";
        },
    },
};
</script>

<style lang="less">
.spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
        width: 100%;
        height: 100%;
    }

    .event {
        width: 100%;
        height: 100%;
        position: absolute;
        top: 0;
        left: 0;
        z-index: 998;
    }

    .mask {
        width: 50%;
        height: 50%;
        background-color: rgba(0, 255, 0, 0.3);
        position: absolute;
        left: 0;
        top: 0;
        display: none;
    }

    .big {
        width: 100%;
        height: 100%;
        position: absolute;
        top: -1px;
        left: 100%;
        border: 1px solid #aaa;
        overflow: hidden;
        z-index: 998;
        display: none;
        background: white;

        img {
            width: 200%;
            max-width: 200%;
            height: 200%;
            position: absolute;
            left: 0;
            top: 0;
        }
    }

    .event:hover ~ .mask,
    .event:hover ~ .big {
        display: block;
    }
}
</style>